interface HasherState {
  buffer: string;
  buflen: number;
  length: number;
  state: number[];
}

export class Md5 {
  // Private Static Variables
  private static stateIdentity = new Int32Array([
    1732584193, -271733879, -1732584194, 271733878
  ]);
  private static buffer32Identity = new Int32Array([
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
  ]);
  private static hexChars = "0123456789abcdef";
  private static hexOut: string[] = [];
  // Permanent instance is to use for one-call hashing
  private static onePassHasher = new Md5();
  private _dataLength = 0;
  private _bufferLength = 0;
  private _state: Int32Array = new Int32Array(4);
  private _buffer: ArrayBuffer = new ArrayBuffer(68);
  private _buffer8: Uint8Array;
  private _buffer32: Uint32Array;

  constructor() {
    this._buffer8 = new Uint8Array(this._buffer, 0, 68);
    this._buffer32 = new Uint32Array(this._buffer, 0, 17);
    this.start();
  }

  /**
   * Hash a UTF-8 string on the spot
   * @param str String to hash
   * @param raw Whether to return the value as an `Int32Array`
   */
  public static hashStr(str: string, raw?: false): string;

  public static hashStr(str: string, raw: true): Int32Array;

  public static hashStr(str: string, raw: boolean = false) {
    return this.onePassHasher.start().appendStr(str).end(raw);
  }

  /**
   * Hash a ASCII string on the spot
   * @param str String to hash
   * @param raw Whether to return the value as an `Int32Array`
   */
  public static hashAsciiStr(str: string, raw?: false): string;

  public static hashAsciiStr(str: string, raw: true): Int32Array;

  public static hashAsciiStr(str: string, raw: boolean = false) {
    return this.onePassHasher.start().appendAsciiStr(str).end(raw);
  }

  private static _hex(x: Int32Array): string {
    const hc = Md5.hexChars;
    const ho = Md5.hexOut;
    let n;
    let offset;
    let j;
    let i;

    for (i = 0; i < 4; i += 1) {
      offset = i * 8;
      n = x[i];
      for (j = 0; j < 8; j += 2) {
        ho[offset + 1 + j] = hc.charAt(n & 0x0f);
        n >>>= 4;
        ho[offset + 0 + j] = hc.charAt(n & 0x0f);
        n >>>= 4;
      }
    }
    return ho.join("");
  }

  private static _md5cycle(
    x: Int32Array | Uint32Array,
    k: Int32Array | Uint32Array
  ) {
    let a = x[0];
    let b = x[1];
    let c = x[2];
    let d = x[3];
    // ff()
    a += (((b & c) | (~b & d)) + k[0] - 680876936) | 0;
    a = (((a << 7) | (a >>> 25)) + b) | 0;
    d += (((a & b) | (~a & c)) + k[1] - 389564586) | 0;
    d = (((d << 12) | (d >>> 20)) + a) | 0;
    c += (((d & a) | (~d & b)) + k[2] + 606105819) | 0;
    c = (((c << 17) | (c >>> 15)) + d) | 0;
    b += (((c & d) | (~c & a)) + k[3] - 1044525330) | 0;
    b = (((b << 22) | (b >>> 10)) + c) | 0;
    a += (((b & c) | (~b & d)) + k[4] - 176418897) | 0;
    a = (((a << 7) | (a >>> 25)) + b) | 0;
    d += (((a & b) | (~a & c)) + k[5] + 1200080426) | 0;
    d = (((d << 12) | (d >>> 20)) + a) | 0;
    c += (((d & a) | (~d & b)) + k[6] - 1473231341) | 0;
    c = (((c << 17) | (c >>> 15)) + d) | 0;
    b += (((c & d) | (~c & a)) + k[7] - 45705983) | 0;
    b = (((b << 22) | (b >>> 10)) + c) | 0;
    a += (((b & c) | (~b & d)) + k[8] + 1770035416) | 0;
    a = (((a << 7) | (a >>> 25)) + b) | 0;
    d += (((a & b) | (~a & c)) + k[9] - 1958414417) | 0;
    d = (((d << 12) | (d >>> 20)) + a) | 0;
    c += (((d & a) | (~d & b)) + k[10] - 42063) | 0;
    c = (((c << 17) | (c >>> 15)) + d) | 0;
    b += (((c & d) | (~c & a)) + k[11] - 1990404162) | 0;
    b = (((b << 22) | (b >>> 10)) + c) | 0;
    a += (((b & c) | (~b & d)) + k[12] + 1804603682) | 0;
    a = (((a << 7) | (a >>> 25)) + b) | 0;
    d += (((a & b) | (~a & c)) + k[13] - 40341101) | 0;
    d = (((d << 12) | (d >>> 20)) + a) | 0;
    c += (((d & a) | (~d & b)) + k[14] - 1502002290) | 0;
    c = (((c << 17) | (c >>> 15)) + d) | 0;
    b += (((c & d) | (~c & a)) + k[15] + 1236535329) | 0;
    b = (((b << 22) | (b >>> 10)) + c) | 0;
    // gg()
    a += (((b & d) | (c & ~d)) + k[1] - 165796510) | 0;
    a = (((a << 5) | (a >>> 27)) + b) | 0;
    d += (((a & c) | (b & ~c)) + k[6] - 1069501632) | 0;
    d = (((d << 9) | (d >>> 23)) + a) | 0;
    c += (((d & b) | (a & ~b)) + k[11] + 643717713) | 0;
    c = (((c << 14) | (c >>> 18)) + d) | 0;
    b += (((c & a) | (d & ~a)) + k[0] - 373897302) | 0;
    b = (((b << 20) | (b >>> 12)) + c) | 0;
    a += (((b & d) | (c & ~d)) + k[5] - 701558691) | 0;
    a = (((a << 5) | (a >>> 27)) + b) | 0;
    d += (((a & c) | (b & ~c)) + k[10] + 38016083) | 0;
    d = (((d << 9) | (d >>> 23)) + a) | 0;
    c += (((d & b) | (a & ~b)) + k[15] - 660478335) | 0;
    c = (((c << 14) | (c >>> 18)) + d) | 0;
    b += (((c & a) | (d & ~a)) + k[4] - 405537848) | 0;
    b = (((b << 20) | (b >>> 12)) + c) | 0;
    a += (((b & d) | (c & ~d)) + k[9] + 568446438) | 0;
    a = (((a << 5) | (a >>> 27)) + b) | 0;
    d += (((a & c) | (b & ~c)) + k[14] - 1019803690) | 0;
    d = (((d << 9) | (d >>> 23)) + a) | 0;
    c += (((d & b) | (a & ~b)) + k[3] - 187363961) | 0;
    c = (((c << 14) | (c >>> 18)) + d) | 0;
    b += (((c & a) | (d & ~a)) + k[8] + 1163531501) | 0;
    b = (((b << 20) | (b >>> 12)) + c) | 0;
    a += (((b & d) | (c & ~d)) + k[13] - 1444681467) | 0;
    a = (((a << 5) | (a >>> 27)) + b) | 0;
    d += (((a & c) | (b & ~c)) + k[2] - 51403784) | 0;
    d = (((d << 9) | (d >>> 23)) + a) | 0;
    c += (((d & b) | (a & ~b)) + k[7] + 1735328473) | 0;
    c = (((c << 14) | (c >>> 18)) + d) | 0;
    b += (((c & a) | (d & ~a)) + k[12] - 1926607734) | 0;
    b = (((b << 20) | (b >>> 12)) + c) | 0;
    // hh()
    a += ((b ^ c ^ d) + k[5] - 378558) | 0;
    a = (((a << 4) | (a >>> 28)) + b) | 0;
    d += ((a ^ b ^ c) + k[8] - 2022574463) | 0;
    d = (((d << 11) | (d >>> 21)) + a) | 0;
    c += ((d ^ a ^ b) + k[11] + 1839030562) | 0;
    c = (((c << 16) | (c >>> 16)) + d) | 0;
    b += ((c ^ d ^ a) + k[14] - 35309556) | 0;
    b = (((b << 23) | (b >>> 9)) + c) | 0;
    a += ((b ^ c ^ d) + k[1] - 1530992060) | 0;
    a = (((a << 4) | (a >>> 28)) + b) | 0;
    d += ((a ^ b ^ c) + k[4] + 1272893353) | 0;
    d = (((d << 11) | (d >>> 21)) + a) | 0;
    c += ((d ^ a ^ b) + k[7] - 155497632) | 0;
    c = (((c << 16) | (c >>> 16)) + d) | 0;
    b += ((c ^ d ^ a) + k[10] - 1094730640) | 0;
    b = (((b << 23) | (b >>> 9)) + c) | 0;
    a += ((b ^ c ^ d) + k[13] + 681279174) | 0;
    a = (((a << 4) | (a >>> 28)) + b) | 0;
    d += ((a ^ b ^ c) + k[0] - 358537222) | 0;
    d = (((d << 11) | (d >>> 21)) + a) | 0;
    c += ((d ^ a ^ b) + k[3] - 722521979) | 0;
    c = (((c << 16) | (c >>> 16)) + d) | 0;
    b += ((c ^ d ^ a) + k[6] + 76029189) | 0;
    b = (((b << 23) | (b >>> 9)) + c) | 0;
    a += ((b ^ c ^ d) + k[9] - 640364487) | 0;
    a = (((a << 4) | (a >>> 28)) + b) | 0;
    d += ((a ^ b ^ c) + k[12] - 421815835) | 0;
    d = (((d << 11) | (d >>> 21)) + a) | 0;
    c += ((d ^ a ^ b) + k[15] + 530742520) | 0;
    c = (((c << 16) | (c >>> 16)) + d) | 0;
    b += ((c ^ d ^ a) + k[2] - 995338651) | 0;
    b = (((b << 23) | (b >>> 9)) + c) | 0;
    // ii()
    a += ((c ^ (b | ~d)) + k[0] - 198630844) | 0;
    a = (((a << 6) | (a >>> 26)) + b) | 0;
    d += ((b ^ (a | ~c)) + k[7] + 1126891415) | 0;
    d = (((d << 10) | (d >>> 22)) + a) | 0;
    c += ((a ^ (d | ~b)) + k[14] - 1416354905) | 0;
    c = (((c << 15) | (c >>> 17)) + d) | 0;
    b += ((d ^ (c | ~a)) + k[5] - 57434055) | 0;
    b = (((b << 21) | (b >>> 11)) + c) | 0;
    a += ((c ^ (b | ~d)) + k[12] + 1700485571) | 0;
    a = (((a << 6) | (a >>> 26)) + b) | 0;
    d += ((b ^ (a | ~c)) + k[3] - 1894986606) | 0;
    d = (((d << 10) | (d >>> 22)) + a) | 0;
    c += ((a ^ (d | ~b)) + k[10] - 1051523) | 0;
    c = (((c << 15) | (c >>> 17)) + d) | 0;
    b += ((d ^ (c | ~a)) + k[1] - 2054922799) | 0;
    b = (((b << 21) | (b >>> 11)) + c) | 0;
    a += ((c ^ (b | ~d)) + k[8] + 1873313359) | 0;
    a = (((a << 6) | (a >>> 26)) + b) | 0;
    d += ((b ^ (a | ~c)) + k[15] - 30611744) | 0;
    d = (((d << 10) | (d >>> 22)) + a) | 0;
    c += ((a ^ (d | ~b)) + k[6] - 1560198380) | 0;
    c = (((c << 15) | (c >>> 17)) + d) | 0;
    b += ((d ^ (c | ~a)) + k[13] + 1309151649) | 0;
    b = (((b << 21) | (b >>> 11)) + c) | 0;
    a += ((c ^ (b | ~d)) + k[4] - 145523070) | 0;
    a = (((a << 6) | (a >>> 26)) + b) | 0;
    d += ((b ^ (a | ~c)) + k[11] - 1120210379) | 0;
    d = (((d << 10) | (d >>> 22)) + a) | 0;
    c += ((a ^ (d | ~b)) + k[2] + 718787259) | 0;
    c = (((c << 15) | (c >>> 17)) + d) | 0;
    b += ((d ^ (c | ~a)) + k[9] - 343485551) | 0;
    b = (((b << 21) | (b >>> 11)) + c) | 0;

    x[0] = (a + x[0]) | 0;
    x[1] = (b + x[1]) | 0;
    x[2] = (c + x[2]) | 0;
    x[3] = (d + x[3]) | 0;
  }

  /**
   * Initialise buffer to be hashed
   */
  public start() {
    this._dataLength = 0;
    this._bufferLength = 0;
    this._state.set(Md5.stateIdentity);
    return this;
  }

  // Char to code point to to array conversion:
  // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/charCodeAt
  // #Example.3A_Fixing_charCodeAt_to_handle_non-Basic-Multilingual-Plane_characters_if_their_presence_earlier_in_the_string_is_unknown

  /**
   * Append a UTF-8 string to the hash buffer
   * @param str String to append
   */
  public appendStr(str: string) {
    const buf8 = this._buffer8;
    const buf32 = this._buffer32;
    let bufLen = this._bufferLength;
    let code;
    let i;

    for (i = 0; i < str.length; i += 1) {
      code = str.charCodeAt(i);
      if (code < 128) {
        buf8[bufLen++] = code;
      } else if (code < 0x800) {
        buf8[bufLen++] = (code >>> 6) + 0xc0;
        buf8[bufLen++] = (code & 0x3f) | 0x80;
      } else if (code < 0xd800 || code > 0xdbff) {
        buf8[bufLen++] = (code >>> 12) + 0xe0;
        buf8[bufLen++] = ((code >>> 6) & 0x3f) | 0x80;
        buf8[bufLen++] = (code & 0x3f) | 0x80;
      } else {
        code =
          (code - 0xd800) * 0x400 + (str.charCodeAt(++i) - 0xdc00) + 0x10000;
        if (code > 0x10ffff) {
          throw new Error(
            "Unicode standard supports code points up to U+10FFFF"
          );
        }
        buf8[bufLen++] = (code >>> 18) + 0xf0;
        buf8[bufLen++] = ((code >>> 12) & 0x3f) | 0x80;
        buf8[bufLen++] = ((code >>> 6) & 0x3f) | 0x80;
        buf8[bufLen++] = (code & 0x3f) | 0x80;
      }
      if (bufLen >= 64) {
        this._dataLength += 64;
        Md5._md5cycle(this._state, buf32);
        bufLen -= 64;
        buf32[0] = buf32[16];
      }
    }
    this._bufferLength = bufLen;
    return this;
  }

  /**
   * Append an ASCII string to the hash buffer
   * @param str String to append
   */
  public appendAsciiStr(str: string) {
    const buf8 = this._buffer8;
    const buf32 = this._buffer32;
    let bufLen = this._bufferLength;
    let i;
    let j = 0;

    for (;;) {
      i = Math.min(str.length - j, 64 - bufLen);
      while (i--) {
        buf8[bufLen++] = str.charCodeAt(j++);
      }
      if (bufLen < 64) {
        break;
      }
      this._dataLength += 64;
      Md5._md5cycle(this._state, buf32);
      bufLen = 0;
    }
    this._bufferLength = bufLen;
    return this;
  }

  /**
   * Append a byte array to the hash buffer
   * @param input array to append
   */
  public appendByteArray(input: Uint8Array) {
    const buf8 = this._buffer8;
    const buf32 = this._buffer32;
    let bufLen = this._bufferLength;
    let i;
    let j = 0;

    for (;;) {
      i = Math.min(input.length - j, 64 - bufLen);
      while (i--) {
        buf8[bufLen++] = input[j++];
      }
      if (bufLen < 64) {
        break;
      }
      this._dataLength += 64;
      Md5._md5cycle(this._state, buf32);
      bufLen = 0;
    }
    this._bufferLength = bufLen;
    return this;
  }

  /**
   * Get the state of the hash buffer
   */
  public getState(): HasherState {
    const s = this._state;

    return {
      buffer: String.fromCharCode.apply(null, Array.from(this._buffer8)),
      buflen: this._bufferLength,
      length: this._dataLength,
      state: [s[0], s[1], s[2], s[3]]
    };
  }

  /**
   * Override the current state of the hash buffer
   * @param state New hash buffer state
   */
  public setState(state: HasherState) {
    const buf = state.buffer;
    const x = state.state;
    const s = this._state;
    let i;

    this._dataLength = state.length;
    this._bufferLength = state.buflen;
    s[0] = x[0];
    s[1] = x[1];
    s[2] = x[2];
    s[3] = x[3];

    for (i = 0; i < buf.length; i += 1) {
      this._buffer8[i] = buf.charCodeAt(i);
    }
  }

  /**
   * Hash the current state of the hash buffer and return the result
   * @param raw Whether to return the value as an `Int32Array`
   */
  public end(raw: boolean = false) {
    const bufLen = this._bufferLength;
    const buf8 = this._buffer8;
    const buf32 = this._buffer32;
    const i = (bufLen >> 2) + 1;

    this._dataLength += bufLen;
    const dataBitsLen = this._dataLength * 8;

    buf8[bufLen] = 0x80;
    buf8[bufLen + 1] = buf8[bufLen + 2] = buf8[bufLen + 3] = 0;
    buf32.set(Md5.buffer32Identity.subarray(i), i);

    if (bufLen > 55) {
      Md5._md5cycle(this._state, buf32);
      buf32.set(Md5.buffer32Identity);
    }

    // Do the final computation based on the tail and length
    // Beware that the final length may not fit in 32 bits so we take care of that
    if (dataBitsLen <= 0xffffffff) {
      buf32[14] = dataBitsLen;
    } else {
      const matches = dataBitsLen.toString(16).match(/(.*?)(.{0,8})$/);
      if (matches === null) {
        return;
      }

      const lo = parseInt(matches[2], 16);
      const hi = parseInt(matches[1], 16) || 0;

      buf32[14] = lo;
      buf32[15] = hi;
    }

    Md5._md5cycle(this._state, buf32);

    return raw ? this._state : Md5._hex(this._state);
  }
}
